Precipitation of tannins and/or proteinaceous substances from liquid media



Um'fled Staffs Patent Q Anilne & Film Corporation,` New York, N. Y., a corporation of Delaware r t `No Drawing. Application October 31,1957

tf Serial No.-`69`3,529 Geminis. (C139-48) The present invention relates to anuimproved method f"`removing tannins and/or` proteinftannin `complexes from `'liquidi'ediacontaining the same. f Y

` The substantial removal or elimination o f tannins and/ 'or'protein-tannin` complexes `from liquid mediums containing the same is highly desirable in order to effect improvement in taste, clarity, purity, stability "and the like.` In the food, beverage and drug industries, it is necessary to remove natural tannin substances suchas tannic acids and tannins, and protein-tannin complexes, For instance, in the preparation of beer fromextracts ofbarley ."a'n'd hops, Wine from pressed grapes, brandy, whiskeyQiruit juices, `tea or coffee, sugar caneextracts, etc. it is necessary to remove tannins or tannic acid.

,As` the art is now practiced, tannins are precipitated front`t`/`t'u"i ')us`` liquid mediums `containing the same by the Iaddition tif-variouscoagulatingand precipitating agents, such" as for 'eitample, `ferrie hydroxide, lead` acetate, 'gelatinjcalfeine' casein, skimmedmilk, activated charcoal and'the'mlike.Y p Y r y n `In"a' majority of ncases, while employing such coagulating and precipitating agents,` the residue of the precipitant or ofltheftannin orjtannicacid remains in the solutineitherfrom the necessity of using an excess of the precip'itant or coagulantffrom metathesis incidental to precipitation, or from incomplete precipitation.` The residue thus remaining is undesirable and even injurious, thus renderingthese methods of precipitationunsuitable for'many purposes. a

t lIhave'di'scovered that naturaltannn substances, i. e. tannc acidfandtannins'and/ortprotein-tannin complexes, are'substantially and in a majority of cases, `,quantitatively precipitated `from liquid media, especially aqueous and alcoholic solutions containing them, by theaddition of afco'agulating or precipitating amount of a polyvinylimidazole- `having th`e`1 following 4general formula:

t wherein n representstheuextent df polymerizationas indicatedv by `the molecular weightwhichmay range from Y 2,875,062 lfatented Feb. 24, `195.9

tion or in methanol solution to yield a water soluble polymer.

. inthe particular operation.

Natural tannin substances such as tannic acids and tannins are readily precipitated from alcohol, alcoholwater and aqueous solutions Icontaining them bythe addition of a precipitating amount of the polyvinylirnida- `zoles. VFor practical purposes `I have found that not only are the tannins and tannic `acid substantially and completely precipitated, but the polyvinylimidazole is likewise substantially and completely precipitated when addedinthis ratio of 2 to 3.5 times the Weight of the natural tannin substances present in said solutions.'Y AThus, the stoichiometric relation of the polyvinylimidazole to tannic acid or tannin in theprecipitate remains'constant regardless of the presence of an excess ofeithe'rfthe tannin substance or the precipitant in the combination. The precipitation of tannic acid from aqueous alcohol or water-alcohol solutionscontaining them by the use of the polyvinylimidazoles `was found to be substantially quantitative, i. e. 99 to 100%. Aftertthe precipitation of the natural tannin substancesthe precipitate can be removed from the liquid medium by centrifuging, iiltering, settling or decanting to yield a clear solution. In the case,` where clarication of the solution is not necessaryand it is merely desired to remove the natural tannin substances, the precipitate can be allowed to remain' in the fluid mixture.

The precipitation or `coagulation of protein-tannin complexes contained in various liquid `mediums con taining the same can be very readily determined by sim` ple 'spot experiments. Eachtliquid medium may require an amountv which may be more or less than another liquidmmedium. 4In other words, the finding of exact amounts Lof the polyvinylimidazole will have to be de-` termined by using minimum and maximum amounts .for achfluid whereby `the exact amount will be indicated The polyvinylimidazole is used to advantage in the removal of'tannin substances and protein-tannin coin'- plexesfrom beer, wine, coiee,` tea, fruit juices, vinegar,

y etc., not only to improve their quality especially at low temperatures but also to remove undesirable tastes and odors. `It may be employed to advantage in clarifying e5 utilized maccordance with the A nins, tannic acid and `pared 'tothe untreated grape-.juice :was most various industrial solutions` and in the preparation of pharmaceutical extracts from materials containing tanvarious complexesof proteins with tannin. n t. d `Thefollowing examples which are merely illustrative will show how the processtof lthe present invention" is to `he",practced.

Example] t, n g -A 5% solution j of; polyvinylimidazole havinga molecularmweight of 160,000 is iirstprepared `intdistilled Water. grape `juice there was added 0.8 cc. of the `and 7.2 cc. of distilled water. tion ,wasA thoroughly stirred and :then placed in larefrigerjator for 20thours. -After allowing towarm to room temperature,the solution was filtered and an 8 cc. aliquot removed., This was then added""to a vtared 4" test tube andtcentrifuged for 1A hour. vlThe liquid `was decanted and the-test `tube dried in a rvacuum at 60V C.tfor 20 hours."` The `Weight of the precipitate was'found foibe 0,0244 gram.` The quality fof, the aliquot` portion/com` remarkable in;.that it was oa clear wine color` Whereas the `grape juice `untreated with polyvinylimidazole was a .murky purple color. t Y

The solu- AExample I was repeated with the exception thaty 0.8 cc. of the aqueous polyvinylimidazole solution was replaced tea, fruit juices, etc. is sufficient to by 2 cc. of the same solution and 7 cc. of water added instead of 7.2 cc. The treated sample was worked as in Example I. The weight ofthe precipitate obtained was 0.0486 gram. The quality. ofthe treated sample, after centrifuging, was of a clear wine color whereas the con trol, i. e. untreated sample was of a murky purple.

From the foregoing examples it becomes clearly mani fest that amounts as little as 0.04 to 0.10 part by weight of the polyvinylimidazole per 100 parts of lbeer, wine, precipitate the tannic acid in substantial quantity, impart clarity and greatly improve the color and brightness.

Example IIIV i To 100 cc. of dry sherry wine there 'was added 2 cc. of aqueous polyvinylirnidazole, solution (containing by weight of the polymer) having a molecular weight of 160,000 Aand mixed thoroughly. A substantial white, curdy precipitate was vformed immediately. Upon settling, a clear` supernatant liquid remained which was much lighter in 'color' than the original sample of wine.

i Example l V To 100 cc.of bourbon (unchilled Schenley, Ancient Age) there was added 2 cc. of an aqueous 5 by weight solution of polyvinylimidazole having a molecular Weight of 160,000 and mixed thoroughly. Upon standing, the whiskey turned cloudy. After centrifuging, asmall white precipitate settled out and the clear supernatant liquid was much lighter in color than the untreated whiskey.

To 50 ml. of freshly ltered beer, which had not been enzyme treated and which had notV been pasteurized, contained in a 4 oz. glass vial, there was added 1 ml. of a 2% aqueous solution of polyvinylimidazole having a molecular weight of 160,000. The precipitate formed in the mixture was allowed to stand' for 48 hours at room temperature. After l2 hours, the precipitate had settled to the bottom of the glass vial and the supernatant liquid was clear after 48 hours. .'The material was filtered through a No. 5 Whatman filter paper. The filtrate' was a clear amber liquid. l l

ans/acca l t 5 5 polyvinylimidazole in The 'sample of the same beer prior -to the addition of the polyvinylimidazole, was iltered through a No. 5 Whatman filter paper and used as a control.

The two liltered beers were cooled'for'20 minutes in a mixture of crushed ice and water. The untreated beer developed a definite haze on cooling, whereas, the treated beer remained clear. v The light transmittancy was determined samples using a Fisher elect'rophotometer.

on Vthe l two whereas the treated beer showed a light transmittancy of 99%. Y

It is to be noted that the precipitation of natural tannin vsubstances occurs by the addition of polyvinyl imidazole in larger amounts up to 3.5 times the quantity of the natural tannin substance present. Thus when an excess of the polyvinylimidazole is not objectionable in the residual liquid medium, amounts from 2.5 to 3.5 parts of the polyvinylimidazole per part by weight of natural tannin substancesY can be added to such solutions or liquid mediums to effect complete precipitation of the natural tannin substances. -Moreover, when it is neeessary to reduce but not to eliminate the natural tannin substances from aqueous or other liquid media, the pro- -portion of the natural tannin substances can be readily regulated 4by adding an amount of the polyvinylirnidazole corresponding to the aforesaid proportion of 2`2.5 times the weight of the natural tannin substance present.

If on the other hand clear solutions aredesired, the polyvinylimidazole-natural tannin substance precipitated The control vbeer (untreated) showed a light transmittancy of .78.7%

can be removed by tiltration, centrifuging, decanting or with suitable filter media or clarifying aids such as silica, aluminum hydroxide gel, fullers earth and the like. Generally however, filtering substances of this type are not required to cause the process of the present invention to operate in a satisfactory manner. In cases where the precipitate is not objectionable such as in rubber latex dispersions, the precipitate 4can be allowed to remain in the iluid mixture.

The temperatures employed in precipitating or coagulating the tannins and/or protein-tannin complexes should not exceed 30-35 C. In lieu of room temperatures and slightly above, temperatures as low as the freezing point of the liquid medium, so long as the liquid medium remainsliquid, may be used. Although not critical the pH `value' ofl the liquid medium whether aqueous, alcohol or alcohol-water should not substantially exceed the limits of 5 to 7.

As observed from the foregoing discussion'and from the illustrative working examples, it becomesfclearly manifest that the concentration of the vpolyvinylimidazoles described herein is not critical. Fairly concentrated solutions of the polyvinylimidazole may be ernployed so long as their viscosity does not interfere with their handling. Relatively concentrated solutions are preferred in order containing tannin,

tannic acid, or protein-tannin complex. Concentrations from l0 to 20% by weight of the the added solution are advantageous to attain the desirable features of the present invention.

I claim: s l

l. The process of precipitating substances selected from the group consisting of natural tannins and proteintannin complexes from liquid media containing the same which comprises adding to the said liquid media, in a precipitating amount, a polyvinylimidazole having a molecular weight of 20,000 to 400,000 and removing the precipitate from the liquid media. l'

2. The process of precipitating natural tannin substances from an aqueous solution containing the same which comprises adding to said solution, in a precipitating amount, a polyvinylimidazole having a molecular weight ranging from 20,000 to 400,000 and removing the precipitate from the aqueous solution.

3. The process for precipitation of natural tannin Vsubstances from fruit juices which comprises adding to said fruit juice, in a precipitating amount, a polyvinylimidazole having a molecular weight ranging from 20,000 to 400,000 and removing the precipitate from the fruit juice.

4. TheV process for precipitation of natural tannin substancesdfrom wine which comprises'addingto said wine, in .a precipitating amount, a polyvinylimidazole having a molecular weight ranging from 20,000 to 400,000 and removing the precipitate from the wine.

5. The process for precipitation of natural tannin substances from whiskey which comprises Aadding to said Whiskey, in a precipitating amount, a polyvinylimidazole References Cited inthe file of this patenta UNITED srATEs PirraNrsYV 2,688,550 McFarlane septfl, 1954 2,811,449 Witwer et al. Oct."29, 1957 to minimize dilution of the solution. 

1. THE PROCESS OF PRECIPITATING SUBSTANCES SELECTED FROM THE GROUP CONSISTING OF NATURAL TANNINS AND PROTEINTANNIN COMPLEXES FROM LIQUID MEDIA CONTAINING THE SAME WHICH COMPRISES ADDING TO THE SAID LIQUID MEDIA, IN A PRECIPITATING AMOUNT, A POLYVINYLIMIDAZOLE HAVING A MOLECULAR WEIGHT OF 20,000 TO 400,000 AND REMOVING THE PRECIPITATE FROM THE LIQUID MEDIA. 